This invention relates to a method of forming a decorative relief pattern on the surface of a substrate by the use of a highly viscous material such as paint to form a layer on the substrate, and a patterned roller to form a pattern on the viscous layer.
Hitherto, various methods of forming patterns on layers of highly viscous material by the use of rollers have been used, but the patterns thus formed are affected by the surface conditions or configuration of the roller, or the pattern engraved thereon, and are also affected by the rotation and direction of movement of the roller. Various rollers hitherto used have plain surfaces or are engraved with a transfer pattern or a relief pattern. When forming a pattern on the article or substrate by the use of such rollers, the roller is usually moved only in a single direction over the article or substrate by mechanical or manual movement, each area of the article or substrate being rolled only once in order to avoid forming directional traces of the direction of the rotary movement of the roller. When a plain surfaced roller is used, the "pattern" thus formed is a flat surface. When a porous elastomer is used, a stippled pattern of delicate relief appearance is formed. In the case of the use of transfer and relief rollers, a flat or slightly uneven print pattern is formed, and in either case the resultant pattern corresponds to the configuration of the surface of the roller and is a series of repeating patterns formed along the direction of rotary movement of the roller. That is, the pattern can be classified as a directional pattern.
In forming the pattern by the above method, it is the normal practice to move the roller to complete a first row and then the roller is displaced by the width thereof at right angles to the direction of movement and the roller is then moved parallel to the former row to complete a second row, and thus, by repeating this motion, patterns can be formed on the entire surface of the article or substrate. In such a method, the boundary lines between the rows become visible, thereby imparting directional traces to the finished pattern. This is more conspicuous when the pattern is formed by transfer printing or reliefing. Accordingly, the article or substrate impressed with the formed pattern sustains a great loss in its commercial value, since directional trances are visible in the direction of the rotary movement of the roller.
The desired pattern may be applied to the article or substrate, for example, a wall element, at a factory, but in practice such work is usually carried out at the location where the article or substrate is used to form the completed structure. In these circumstances, the design is usually applied by the manual use of a roller. However, depending on the prevailing circumstances and other factors, it may be sometimes very difficult to move the roller in a single direction over the entire surface to be patterned and, as a result, to form the desired pattern uniformly over the whole surface of a wall element with conventional rollers. This is particularly so when a wide surface area should be patterned. To overcome this difficulty it is an ordinary practice to use a roller made of a porous elastomer. With this roller, however, it is very difficult to form the pattern uniformly over the whole area, thus necessitating a modification of the pattern from time to time by varying the direction of application of the roller or by overlapping the `runs` of the roller. Such practices of course give rise to directional traces in the pattern as described above. Furthermore, overlapping applications of the roller are apt to cause an undesirable roping phenomenon (this is linear unevenness formed on highly viscous materials in the direction of rotary movement of the roll), thus inhibiting the uniform formation of the desired pattern.
When using highly viscous materials for the pattern forming material and forming the pattern by the rotary application of an ordinary roller, there have therefore been drawbacks such that the formed pattern is directly affected by the shape of the surface of the roller, and the pattern formation may present undesirable phenomena depending on the conditions of application of the roller.